The present disclosure relates to a printer in which a thermal head is mounted.
Tape printers are known that perform printing on a tape discharged from a tape cassette contained inside a housing and that discharge the printed tape to the outside. The tape printers include a printer that uses a thermal head to print directly on a heat-sensitive tape and a printer that uses a thermal head to print by transferring from an ink ribbon to a tape. In a printer in which a thermal head is mounted, temperature control is required for each of heating elements included in the thermal head, in order to print, without blurring, a dot that is to be printed and not to print a dot that is not to be printed. With the temperature control for each of the heating elements included in the thermal head, within a print cycle during which one print dot is formed on a printing medium, there exist a heating period, during which main pulses are applied in order to heat the heating element and perform the printing, and a non-heating period for cooling the heated heating element.
When the printing starts, and even when an isolated print dot is formed on the printing medium during the printing, even if the heating element is heated by the applying of the main pulses, a portion of the heat may escape to the area around the heating element, so the heat that is generated may be slightly insufficient. Furthermore, even if the heating element is heated by the applying of the main pulses, when the heating elements that are adjacent to the heated heating element do not perform printing, the heat from the heated heating element may escape to the heating elements that do not perform printing, so in the same manner, the heat that is generated may be slightly insufficient. Moreover, even if the heating element is heated by the applying of the main pulses, when that particular heating element was not heated during the immediately preceding print cycle, the temperature of the heating element when the main pulses start to be applied may be lower than it would be if the heating element had been heated during the immediately preceding print cycle, and the increase in the temperature of the heating element may be delayed, so the heat that is generated may be slightly insufficient.
Accordingly, a printer has been proposed that uses a thermal head that applies sub-pulses that provide auxiliary heating to the heating element during the print cycle in order to compensate for the insufficiency of the heat that is generated (for example, refer to Patent Literature 1). In the printer, a period for the auxiliary heating by the sub-pulses may be added directly after the period for the heating by the main pulses. Therefore, the period for the heating by the main pulses, the period for the heating by the sub-pulses, and the non-heating period may be included in a single print cycle.
However, as the printing speed is increased, the print cycle may be shortened. It may therefore be necessary to make the periods for the heating by the main pulses and the sub-pulses shorter in accordance with the shortened print cycle. That may solve the time problem, but in order to heat the heating elements such that insufficiency in the amounts of heat that is generated does not occur in the shortened heating periods, it is necessary either to increase the applied voltage or to reduce the resistance values of the heating elements of the thermal head and to increase the electric current that flows to the heating elements of the thermal head. In order to do that, it becomes necessary to increase the voltage withstanding capacity and the current capacity of the integrated circuits for the drive circuit for the thermal head.
It is conceivable that the efficiency with which the heat that is generated by the heating elements of the thermal head is conducted to the printing medium could be improved. In order to do that, it may be necessary to improve the performance of the thin film portion of the thermal head that includes the heating elements in conducting heat to the printing medium. However, no matter which solution is implemented, an increase in cost may not be avoided.